The Finnish Border Guard stated on Friday that it suspects four Russian military planes violated Finland’s airspace on Monday. This comes after Finland’s Ministry of Defence suspected the airspace violation of one Russian military plane on Monday.

The suspected violation violated Finland’s airspace by 2.5 km and involved a four-plane division. The Finnish Border Guard stated that the suspected violation will continue to be investigated, and Finland’s Minister of Defence Antti Häkkäen stated that the ministry takes the suspected violation very seriously.

According to the Institute for the Study of War, Russia did not respond to Finland’s suspected violation. Nonetheless, Russia’s defense ministry announced on Monday that Russian planes flew over the neutral waters of the Barents, Baltic and Norwegian seas. Russia’s defense ministry also said that all of the Russian Aerospace Forces’ flights are conducted in line with international rules.

Finland previously accused Russia of violating its airspace in April and May 2022. Experts then warned that Finland may be subjected to Russian interference if the country decided to join the North Atlantic Treaty Organization (NATO). Finland became the 31st member state of NATO on April 4, 2023, after the Turkish Parliament ratified Finland’s membership bid. The objective of NATO is to “safeguard the Allies’ freedom and security by political and military means.” Under Article 5 of the North Atlantic Treaty, an attack on one member is considered an attack against all members.

Previously, on April 4, the Finnish Ministry of Interior announced that it would extend the closure of crossing stations on its land border with Russia until further notice. In addition, it would also close the water traffic border crossings at Haapasaari, the port of Nuijamaa and Santio, on April 15. The diplomatic relationship between Finland and Russia has been deteriorating since Finland abandoned its long-held stance of military non-alignment and joined NATO. Russia previously criticized Finland’s “politicized attitude” toward the border and disregard of bilateral discussions between border forces.